U.S. patent number 5,933,170 [Application Number 08/735,445] was granted by the patent office on 1999-08-03 for ink jet print head.
This patent grant is currently assigned to NGK Insulators, Ltd., Seiko Epson Corporation. Invention is credited to Kohei Kitahara, Hideo Masumori, Hideaki Sonehara, Nobuo Takahashi, Yukihisa Takeuchi.
United States Patent |
5,933,170 |
Takeuchi , et al. |
August 3, 1999 |
Ink jet print head
Abstract
An ink jet print head is disclosed which includes an ink nozzle
member with nozzles, an ink pump member disposed on the ink nozzle
member and having ink chambers formed behind the respective
nozzles, and piezoelectric/electrostrictive elements each disposed
on a wall defining the corresponding ink chamber, for deforming the
wall to change a pressure of the ink chamber, whereby the ink in
the ink chamber is jetted through the corresponding nozzle. The ink
pump member consists of a spacer plate having windows which are
closed by a closure plate and a connecting plate disposed on the
spacer plate, so as to give the respective ink chambers. The
connecting plate has communication holes through which the ink
chambers communicate with the nozzles. The spacer plate, closure
plate and connecting plate are formed from respective ceramic green
sheets, which are laminated on each other and fired into an
integral ceramic structure as the ink pump member. The
piezoelectric/electrostrictive element includes a pair of
electrodes and a piezoelectric/electrostrictive layer, which are
formed by a film-forming method on an outer surface of the closure
plate.
Inventors: |
Takeuchi; Yukihisa (Aichi-ken,
JP), Masumori; Hideo (Anjo, JP), Takahashi;
Nobuo (Owariasahi, JP), Sonehara; Hideaki (Suwa,
JP), Kitahara; Kohei (Shiojiri, JP) |
Assignee: |
NGK Insulators, Ltd.
(JP)
Seiko Epson Corporation (JP)
|
Family
ID: |
26429215 |
Appl.
No.: |
08/735,445 |
Filed: |
January 2, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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066193 |
May 25, 1993 |
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Foreign Application Priority Data
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May 27, 1992 [JP] |
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4-160204 |
Mar 22, 1993 [JP] |
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5-087996 |
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Current U.S.
Class: |
347/71 |
Current CPC
Class: |
B41J
2/1642 (20130101); B41J 2/1632 (20130101); B41J
2/1646 (20130101); B41J 2/14233 (20130101); B41J
2/1637 (20130101); B41J 2/1643 (20130101); B41J
2/161 (20130101); B41J 2/1623 (20130101); B41J
2002/14387 (20130101) |
Current International
Class: |
B41J
2/16 (20060101); B41J 2/14 (20060101); B41J
002/045 () |
Field of
Search: |
;347/68-71
;310/330,365 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0426473 |
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May 1991 |
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EP |
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0443628 |
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Aug 1991 |
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EP |
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3628346 |
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Feb 1988 |
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DE |
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58-116163 |
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Jul 1983 |
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JP |
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60-232967 |
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Nov 1985 |
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JP |
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62-101455 |
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May 1987 |
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JP |
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62-213399 |
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Sep 1987 |
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JP |
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63-149159 |
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Jun 1988 |
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JP |
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3-128681 |
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May 1991 |
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JP |
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WO 89/07752 |
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Aug 1989 |
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WO |
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Primary Examiner: Fuller; Benjamin R.
Assistant Examiner: Hallacher; Craig A.
Attorney, Agent or Firm: Parkhurst & Wendel, L.L.P.
Parent Case Text
This is a Continuation of application Ser. No. 08/066,193 filed May
25, 1993, now abandoned.
Claims
What is claimed is:
1. An ink jet print head comprising:
an ink nozzle member having a plurality of nozzles through which
fine particles of ink are jetted;
an ink pump member disposed on and bonded to said ink nozzle
member, said ink pump member having a plurality of ink chambers
formed behind the respective nozzles of said ink nozzle member,
said ink pump member comprising a spacer plate having a plurality
of windows which provide said ink chambers, respectively, a closure
plate disposed on one of opposite major surfaces of said spacer
plate remote from said ink nozzle member, for closing one of
opposite openings of each of said windows, and a connecting plate
disposed on the other of said opposite major surfaces of said
spacer plate, for closing the other of said opposite openings of
said each of said windows, said connecting plate having a plurality
of first communication holes located behind the respective nozzles
of said ink nozzle member, for communicating said ink chambers with
the nozzles; said spacer plate, said closure plate and said
connecting plate being formed from ceramic green sheets which are
laminated on each other and fired into an integral ceramic
structure as said ink pump member; and
a plurality of piezoelectric/electrostrictive elements each
disposed on a wall partially defining the corresponding one of said
ink chambers, for deforming said wall so as to change a pressure of
the corresponding ink chamber, whereby the ink in the ink chamber
is jetted through the corresponding one of said plurality of
nozzles, each of said piezoelectric/electrostrictive elements
comprising a piezoelectric/electrostrictive unit consisting of a
pair of electrodes and a piezoelectric/electrostrictive layer,
which are formed by a film-forming method on an outer surface of
said closure plate of said ink pump member, such that said
piezoelectric/electrostrictive layer is interposed between said
pair of electrodes, wherein
said ink nozzle member has an ink supply channel through which the
ink is fed to said ink chambers of said ink pump member, and a
plurality of orifices for guiding the ink from said ink supply
channel to the respective ink chambers, said orifices being open on
an outer surface of the ink nozzle member on which the ink pump
member is superposed, said connecting plate of the ink pump member
having a plurality of second communication holes located adjacent
the respective orifices of the ink nozzle member, said second
communication holes communicating the ink chambers with the
respective orifices.
2. An ink jet print head as defined in claim 1, wherein said first
and second communication holes have a diameter which is smaller
than a width dimension of each of said ink chambers.
3. An ink jet print head as defined in claim 1, wherein said ink
nozzle member consists of a nozzle plate having said plurality of
nozzles, a channel plate having a window formed therethrough, and
an orifice plate having said plurality of orifices, said window of
said channel plate being closed by said nozzle plate and said
orifice plate so as to form said ink supply channel within said ink
nozzle member.
4. An ink jet print head as defined in claim 3, wherein said
orifice plate further has a supply port through which the ink is
supplied to said ink supply channel.
5. An ink jet print head as defined in claim 3, wherein said
orifice plate has a plurality of first through-holes communicating
with said first communication holes of said connecting plate,
respectively, and said channel plate has a plurality of second
through-holes communicating with said nozzles of said nozzle plate,
respectively, said first through-holes being held in communication
with said second through-holes, said ink chambers communicating
with the respective nozzles through the first communication holes
and the first and second through-holes.
6. An ink jet print head as defined in claim 5, wherein said first
and second through-holes have a diameter which is larger than a
diameter of said nozzles.
7. An ink jet print head as defined in claim 1, wherein said ink
pump member is comprises of alumina or zirconia.
8. An ink jet print head as defined in claim 1, wherein said
connecting plate of said ink pump member has a thickness of not
smaller than 10 .mu.m.
9. An ink jet print head as defined in claim 1, wherein said spacer
plate of said ink pump member has a thickness of not smaller than
50 .mu.m.
10. An ink jet print head as defined in claim 1, wherein said
closure plate is comprised of a ceramic material containing
partially or fully stabilized zirconia as a major component.
11. An ink jet print head as defined in claim 1, wherein said
film-forming method for forming said electrodes and said
piezoelectric/electrostrictive layer is selected from the group
consisting of: screen printing, spraying, dipping, coating,
ion-beam method, sputtering, vacuum vapor deposition, ion plating,
CVD and plating.
12. An ink jet print head comprising:
an ink nozzle member having a plurality of nozzles through which
fine particles of ink are jetted;
an ink pump member disposed on and bonded to said ink nozzle
member, said ink pump member having a plurality of ink chambers
formed behind the respective nozzles of said ink nozzle member,
said ink pump member comprising a spacer plate having a plurality
of windows which provide said ink chambers, respectively, a closure
plate disposed on one of opposite major surfaces of said spacer
plate remote from said ink nozzle member, for closing one of
opposite openings of each of said windows, and a connecting plate
disposed on the other of said opposite major surfaces of said
spacer plate, for closing the other of said opposite openings of
said each of said windows, said connecting plate having a plurality
of first communication holes located behind the respective nozzles
of said ink nozzle member, for communicating said ink chambers with
the nozzles; said spacer plate, said closure plate and said
connecting plate being formed from ceramic green sheets which are
laminated on each other and fired into an integral ceramic
structure as said ink pump member; said closure plate having a
thickness of not larger than 50 .mu.m; and
a plurality of piezoelectric/electrostrictive elements each
disposed on a wall partially defining the corresponding one of said
ink chambers, for deforming said wall so as to change a pressure of
the corresponding ink chamber, whereby the ink in the ink chamber
is jetted through the corresponding one of said plurality of
nozzles, each of said piezoelectric/electrostrictive elements
comprising a piezoelectric/electrostrictive unit consisting of a
pair of electrodes and a piezoelectric/electrostrictive layer,
which are formed by a film-forming method on an outer surface of
said closure plate of said ink pump member, such that said
piezoelectric/electrostrictive layer is interposed between said
pair of electrodes.
13. An ink jet print head as defined in claim 12, wherein said ink
pump member is comprised of alumina or zirconia.
14. An ink jet print head as defined in claim 12, wherein said
connecting plate of said ink pump member has a thickness of not
smaller than 10 .mu.m.
15. An ink jet print head as defined in claim 12, wherein said
spacer plate of said ink pump member has a thickness of not smaller
than 50 .mu.m.
16. An ink jet print head as defined in claim 12, wherein said
closure plate is comprised of a ceramic material containing
partially or fully stabilized zirconia as a major component.
17. An ink jet print head as defined in claim 12, wherein said
film-forming method for forming said electrodes and said
piezoelectric/electrostrictive layer is selected from the group
consisting of: screen printing, spraying, dipping, coating,
ion-beam method, sputtering, vacuum vapor deposition, ion plating,
CVD and plating.
18. An ink jet print head comprising:
an ink nozzle member having a plurality of nozzles through which
fine particles of ink are jetted;
an ink pump member disposed on and bonded to said ink nozzle
member, said ink pump member having a plurality of ink chambers
formed behind the respective nozzles of said ink nozzle member,
said ink pump member comprising a spacer plate having a plurality
of windows which provide said ink chambers, respectively, a closure
plate disposed on one of opposite major surfaces of said spacer
plate remote from said ink nozzle member, for closing one of
opposite openings of each of said windows, and a connecting plate
disposed on the other of said opposite major surfaces of said
spacer plate, for closing the other of said opposite openings of
said each of said windows, said connecting plate having a plurality
of first communication holes located behind the respective nozzles
of said ink nozzle member, for communicating said ink chambers with
the nozzles; said spacer plate, said closure plate and said
connecting plate being formed from ceramic green sheets which are
laminated on each other and fired into an integral ceramic
structure as said ink pump member; and
a plurality of piezoelectric/electrostrictive elements each
disposed on a wall partially defining the corresponding one of said
ink chambers, for deforming said wall so as to change a pressure of
the corresponding ink chamber, whereby the ink in the ink chamber
is jetted through the corresponding one of said plurality of
nozzles, each of said piezoelectric/electrostrictive elements
comprising a piezoelectric/electrostrictive unit consisting of a
pair of electrodes and a piezoelectric/electrostrictive layer,
which are formed by a film-forming method on an outer surface of
said closure plate of said ink pump member, such that said
piezoelectric/electrostrictive layer is interposed between said
pair of electrodes, wherein an outer surface of said connecting
plate to which said ink nozzle member is bonded has a maximum
waviness of not larger than 50 .mu.m as measured along a reference
length of 8 mm.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an ink jet print head,
and more particularly to such an ink jet print head which has a
novel structure that assures improved and stable ink-jetting
characteristics or capability, and which is available at a reduced
cost.
2. Discussion of the Prior Art
In the recent market of printers used as an output device of a
computer or others, there is a rapidly increasing demand for an ink
jet printer which operates quietly at a relatively low cost. The
ink jet printer includes an ink jet print head which is generally
adapted to raise the pressure in an ink chamber filled with a mass
of ink, to thereby jet or discharge fine ink particles from nozzles
so as to effect printing.
There is known one type of the ink jet print head which has a
piezoelectric/electrostrictive element disposed on a wall of the
ink chamber, as means for raising the pressure in the ink chamber
as described above. In this type of print head, a volume of the ink
chamber is changed upon energization and displacement of the
piezoelectric/electrostrictive element. The ink jet print head of
this type is advantageous in reduced consumption of electric power,
as compared with another type of ink jet print head which is
adapted to heat the ink by a heater disposed in the ink chamber, to
generate minute bubbles used for jetting the fine ink
particles.
Referring to FIGS. 5 and 6 showing an example of the above type of
the ink jet print head, a metallic nozzle plate 4 having a
plurality of nozzles 2, a metallic orifice plate 8 having a
plurality of orifices 6, and a channel plate 10 are superposed on
each other such that the channel plate 10 is interposed between the
plates 4, 8, and these plates 4, 8, 10 are bonded together into an
ink nozzle member 16. In this ink nozzle member 16, there are
formed a plurality of ink discharge channels 12 for leading or
guiding an ink material to the respective nozzles 2, and at least
one ink supply channel 14 for leading or supplying the ink material
to the orifices 6. The ink jet print head further includes an ink
pump member 24 which consists of two plates 18, 20 made of metal or
synthetic resin and formed in lamination on the ink nozzle member
16. The ink pump member 24 has a plurality of voids 22 which
correspond to the nozzles 2 and orifices 6. With this ink pump
member 24 superposed on and bonded to the ink nozzle member 16,
each of the voids 22 provides an ink chamber 26 formed behind the
corresponding nozzle and orifice 2, 6. The ink jet print head also
includes a plurality of piezoelectric/electrostrictive elements 28
each of which is secured to a wall of the corresponding ink chamber
26 remote from the ink nozzle member 16.
In producing the above type of ink jet print head, however, small
pieces of the piezoelectric/electrostrictive elements 28 must be
bonded to the walls of the respective ink chambers 26, which makes
it extremely difficult to render the resulting print head
sufficiently small-sized. Further, the bonding of the
piezoelectric/electrostrictive elements 28 inevitably pushes up the
cost of manufacture of the print head, and makes it difficult for
the elements 28 to maintain sufficiently high reliability.
In the production of the above-described ink jet print head,
another problem arises when the ink nozzle member 16 and the ink
pump member 24 are bonded together. Namely, the spacing between the
adjacent voids 22, 22 formed in the print head, that is, the
thickness "t" of a partition wall 30 which separates the adjacent
voids from each other, is considerably small, more precisely, about
1 mm or smaller. Such a small spacing between the voids 22 makes it
extremely difficult to bond the ink nozzle member 16 and the ink
pump member 24 to each other.
More specifically, an adhesive used for bonding the ink nozzle
member 16 and the ink pump member 24 is likely to overflow onto the
opposite surfaces of the partition wall 30. Therefore, the ink
chambers 26 and/or ink flow channels including the ink supply and
discharge channels 12, 14 and orifices 6 may be deformed, whereby
the ink-jetting characteristics of the print head may deteriorate,
resulting in reduced quality and yield of the products (print
heads).
If the amount of the adhesive applied is reduced to avoid its
overflow as described above, it is likely that the ink nozzle
member 16 and ink pump member 24 are insufficiently or poorly
bonded together at some portions of the interface of the members
16, 24. This may result in incomplete sealing between the adjacent
ink chambers 26, 26, causing leakage of the pressures of the ink
chambers 26, 26 and consequent crosstalk, for example. The partial
or insufficient bonding may also leave gaps between the bonding
surfaces of the members 16, 24, resulting in pressure loss upon
pressurizing of the ink chambers 26 due to the air remaining in the
gaps. Consequently, the ink-jetting characteristics of the print
head may be lowered.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an
ink jet print head in which an ink nozzle member and an ink pump
member can be easily bonded to each other, to alleviate or
eliminate the above problems due to incomplete bonding of the
members or overflow of an adhesive from their bonding surfaces,
thereby assuring excellent ink-jetting characteristics with high
stability. It is also an object of the invention to provide such an
ink jet print head which can be easily produced with improved
efficiency, and which is sufficiently small-sized.
The above object may be accomplished according to the principle of
the present invention, which provides an ink jet print head
comprising: an ink nozzle member having a plurality of nozzles
through which fine particles of an ink are jetted; an ink pump
member disposed on and bonded to the ink nozzle member, the ink
pump member having a plurality of ink chambers formed behind the
respective nozzles of the ink nozzle member, the ink pump member
consisting of a spacer plate having a plurality of windows which
provide the ink chambers, respectively, a closure plate disposed on
one of opposite major surfaces of the spacer plate remote from the
ink nozzle member, for closing one of opposite openings of each of
the windows, and a connecting plate disposed on the other major
surface of the spacer plate, for closing the other opening of each
window, the connecting plate having a plurality of first
communication holes located behind the respective nozzles of the
ink nozzle member, for communicating the ink chambers with the
respective nozzles, the spacer plate, the closure plate and the
connecting plate being formed from respective ceramic green sheets
which are laminated on each other and fired into an integral
ceramic structure as the ink pump member; and a plurality of
piezoelectric/electrostrictive elements each disposed on a wall
partially defining the corresponding one of the ink chambers, for
deforming the wall so as to change a pressure of the corresponding
ink chamber, whereby the ink in the ink chamber is jetted through
the corresponding one of the plurality of nozzles, each of the
piezoelectric/electrostrictive elements comprising a
piezoelectric/electrostrictive portion consisting of a pair of
electrodes and a piezoelectric/electrostrictive layer, which are
formed by a film-forming method on an outer surface of the closure
plate of the ink pump member, such that the
piezoelectric/electrostrictive layer is interposed between the pair
of electrodes.
In the ink jet print head constructed according to the present
invention, an ink flow channel through which the ink flows through
the print head is provided with a remarkably improved seal at an
interface between the ink pump member and the ink nozzle member.
This leads to an effectively improved and stable quality of the
print heads produced.
Further, according to the present invention, the
piezoelectric/electrostrictive elements can be easily formed by a
film-forming method with considerably high efficiency. Therefore,
the present print head can be produced with further improved
quality and improved production efficiency, while permitting
reduction of the size thereof.
In a preferred form of the present invention, the ink nozzle member
has an ink supply channel through which the ink is fed to the ink
chambers of the ink pump member, and a plurality of orifices for
guiding the ink from the ink supply channel to the respective ink
chambers. The orifices are open on an outer surface of the ink
nozzle member on which the ink pump member is superposed. Further,
the connecting plate of the ink pump member has a plurality of
second communication holes located adjacent the respective orifices
of the ink nozzle member, for communicating the ink chambers with
the respective orifices.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and optional objects, features and advantages of the
present invention will be better understood by reading the
following detailed description of presently preferred embodiments
of the invention, when considered in connection with the
accompanying drawings, in which:
FIG. 1 is a vertical cross sectional view showing one embodiment of
an ink jet print head of the present invention;
FIG. 2 is a cross sectional view taken along line 2--2 of FIG.
1;
FIG. 3 is an exploded perspective view explaining the construction
of the ink jet print head of FIG. 1;
FIG. 4 is a vertical cross sectional view corresponding to that of
FIG. 1, showing another embodiment of an ink jet print head of the
present invention;
FIG. 5 is a vertical cross sectional view showing one example of
conventional ink jet print head;
FIG. 6 is a cross sectional view taken along line 6--6 of FIG. 5;
and
FIG. 7 is a cross sectional view corresponding to that of FIG. 2,
showing a modification of first and second communication holes of
the ink jet print head of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 2 schematically showing an ink jet print
head 40 as one preferred embodiment of the present invention, and
to FIG. 3 which is an exploded perspective view of the print head
40, an ink nozzle member 42 and an ink pump member 44 are bonded
together to form an integral structure of the ink jet print head
40. In this print head 40, an ink material is supplied to a
plurality of ink chambers 46 formed in the ink pump member 44, and
is jetted or discharged from a plurality of nozzles 54 formed
through the ink nozzle member 42.
More specifically, the ink nozzle member 42 consists of a nozzle
plate 48 and an orifice plate 50 having a relatively small
thickness, and a channel plate 52 interposed between these plates
48, 50. The nozzle plate 48 and the orifice plate 50 are integrally
bonded to the channel plate 52 by means of an adhesive.
The nozzle plate 48 has a plurality of nozzles 54 (three in this
embodiment) formed therethrough, for permitting jets of fine ink
particles, while the orifice plate 50 and the channel plate 52 have
respective through-holes 56, 57 formed through the thicknesses
thereof. These through-holes 56, 57 are aligned with the respective
nozzles 54 as viewed in the direction of the thickness of the
plates 48, 50, 52, and have a diameter which is larger by a given
value than that of the nozzles 54.
The orifice plate 50 further has a plurality of orifices 58 (three
in this embodiment) formed therethrough, for permitting flow of the
ink into to the respective ink chambers 46. The channel plate 52 is
formed with a window 60 which is closed at its opposite openings by
the nozzle plate 48 and orifice plate 50, respectively, whereby an
ink supply channel 62 communicating with the orifices 58 is defined
by the channel plate 52, the nozzle plate 48 and the orifice plate
50. The orifice plate 50 further has a supply port 64 through which
the ink is fed from an ink reservoir into the ink supply channel
62.
While the material used for the plates 48, 50, 52 of the ink nozzle
member 42 is not particularly limited, these plates 48, 50, 52 are
preferably made of a plastic, or a metal such as nickel or
stainless steel, which enables the nozzles 54 and orifices 58 to be
formed in the respective plates 48, 50 with high accuracy. Each of
the orifices 58 is desirably formed in tapered shape such that the
diameter of the orifice 58 is reduced in the direction of flow of
the ink (i.e., the direction from the ink supply channel 62 toward
the ink chambers 46), as shown in FIG. 1 by way of example, so as
to function as a check valve for inhibiting the ink from flowing in
the reverse direction.
The ink pump member 44 consists of a closure plate 66 and a
connecting plate 68 having a relatively small thickness, and a
spacer plate 70 interposed between these plates 66, 68. These
plates 66, 68, 70 are superposed on each other and formed
integrally into the ink pump member 44 in a manner as described
later.
The connecting plate 68 has first communication holes 72 and second
communication holes 74 formed therethrough, which are respectively
aligned with the through-holes 56 and orifices 58 formed in the
orifice plate 50, as viewed in the direction of thickness of the
plates 68, 50. The diameter of the first communication holes 72 is
substantially equal to or slightly larger than that of the
through-holes 56, while the diameter of the second communication
holes 74 is larger by a given value than that of the orifices
58.
The spacer plate 70 has a plurality of rectangular windows 76
formed therethrough. The spacer plate 70 is superposed on the
connecting plate 68 such that each of the windows 76 communicates
with the corresponding first and second communication holes 72, 74
formed in the connecting plate 68.
On one of the opposite major surfaces of the spacer plate 70 remote
from the connecting plate 68 is superposed on the above-indicated
closure plate 66 for closing openings of the windows 76. In this
arrangement, the ink chambers 46 are formed within the ink pump
member 44, such that the chambers 46 communicate with an exterior
space through the first and second communication holes 72, 74.
The ink pump member 44 is formed as an integrally formed fired
ceramic structure. That is, in the process of producing the ink
pump member 44, green sheets are initially formed by using a slurry
that is prepared from ceramic materials, binders, liquid solvents
and others, by means of a generally used device such as a doctor
blade device or a reverse roll coater. Then, the green sheets are
subjected to suitable processing such as cutting, machining or
punching, as needed, so as to form the windows 76 and the first and
second communication holes 72, 74. Thus, there are formed
precursors for the plates 66, 68, 70. These precursors are then
laminated on each other and fired into an integral ceramic body as
the ink pump member 44.
While the ceramic material used for forming the ink pump member 44
is not particularly limited, alumina, zirconia or the like may be
favorably employed in view of its formability and other properties.
The closure plate 66 preferably has a thickness of 50 .mu.m or
smaller, more preferably, within a range of about 3 to 12 .mu.m.
The connecting plate 68 preferably has a thickness of 10 .mu.m or
larger, more preferably, 50 .mu.m or larger. The spacer plate 70
preferably has a thickness of 50 .mu.m or larger, more preferably,
100 .mu.m or larger.
The above-described ink pump member 44, which is formed as an
integral fired ceramic structure, does not require any particular
adhesive treatment for bonding the plates 66, 68, 70 together.
Accordingly, complete and secure sealing can be achieved at the
interfaces between the closure plate 66 and spacer plate 70 and
between the connecting plate 68 and spacer plate 70.
In addition, the ink pump member 44 can be produced with improved
efficiency, due to the presence of the connecting plate 68. Namely,
it is generally difficult to handle a laminar structure consisting
of thin, flexible green sheets, and fracture of the laminar
structure and abnormal deformation of a resultant fired body tend
to occur due to strains induced in the laminar structure when it is
inadvertently supported upon its setting on a furnace. In the
instant embodiment, however, the laminar structure including the
connecting plate 68 exhibits an enhanced rigidity due to the
presence of the plate 68, assuring improved handling ease thereof,
while reducing the possibility of occurrence of defects due to
handling failure, as compared with when the structure does not
include the connecting plate 68. Further, it is normally impossible
to handle a laminar structure consisting only of the closure plate
66 and spacer plate 70 where the ink chambers 46 are formed with
high density in the ink pump member 44, that is, where the ink pump
member 44 includes a comparatively large number of ink chambers 46.
In the instant embodiment, however, the connecting plate 68 makes
it possible to handle the laminar structure even in the
above-described situation.
While the configuration of the ink pump member 44 varies depending
upon various factors relating to production of this member 44, it
is desirable that the surface of the ink pump member 44 which is to
be bonded to the ink nozzle member 42, that is, the outer surface
of the connecting plate 68, is made even or smooth. The evenness of
the relevant surface of the ink pump member 44 is suitably
controlled so that the surface has the maximum waviness of not
larger than 50 .mu.m as measured along a reference length of 8 mm,
by means of a roughness measuring system. Desirably, the maximum
waviness of the relevant surface is not larger than 25 .mu.m, more
desirably, not larger than 10 .mu.m. As a means for achieving the
above degree of surface evenness, the fired ceramic body which
gives the ink pump member 44 may be subjected to machining such as
lapping or surface grinding.
On the ink pump member 44, more precisely, on the outer surface of
the closure plate 66, there are formed
piezoelectric/electrostrictive elements 78 which correspond to the
respective ink chambers 46 formed in the member 44. Each of the
piezoelectric/electrostrictive elements 78 has a
piezoelectric/electrostrictive unit consisting of a lower electrode
77, a piezoelectric/electrostrictive layer 79, and an upper
electrode 75, which are formed in lamination on the closure plate
66, by a suitable film-forming method. As the
piezoelectric/electrostrictive element 78 of the instant
embodiment, it is particularly preferable to employ a
piezoelectric/electrostrictive element as proposed in co-pending
U.S. patent application No. 07/912,920 assigned to the same
assignee as the present patent application.
More specifically, the closure plate 66, which serves as a
substrate for the piezoelectric/electrostrictive elements 78, is
suitably formed by a ceramic substrate made of a material whose
major component is zirconia having a crystal phase that is
partially or fully stabilized by a suitable compound or compounds.
The term "partially or fully stabilized zirconia" used herein
should be interpreted to mean zirconia whose crystal phase is
partially or fully stabilized, so that the crystal phase partially
undergoes or does not undergo phase transformations, respectively,
upon application of heat, stress or the like thereto.
The above-indicated compound or compounds for stabilizing the
zirconia is selected from the group consisting of: yttrium oxide;
cerium oxide; magnesium oxide; and calcium oxide. The zirconia is
partially or fully stabilized as desired, by addition of at least
one of these compounds, that is, a selected one of the
above-indicated oxides or a selected combination of two or more of
these oxides. It is desirable to stabilize the zirconia by adding 2
to 7 mole % of yttrium oxide, or 6 to 15 mole % of cerium oxide, or
5 to 12 mole % of magnesium oxide or calcium oxide. It is
particularly recommended to use yttrium oxide in an amount of 2 to
7 mole %, more preferably, 2 to 4 mole %, so as to partially
stabilize the zirconia. With the addition of the yttrium oxide in
the above range, the zirconia has a primary crystal phase which is
partially stabilized as a tetragonal phase or a combination of a
cubic phase and the tetragonal phase, to provide the ceramic
substrate (closure plate 66) having excellent properties. Further,
the average crystal grain size of the ceramic substrate is
preferably controlled to within a range of 0.05 .mu.m-2 .mu.m, more
preferably, to 1 .mu.m or smaller, so as to ensure the presence of
the tetragonal phase and assure a sufficiently large mechanical
strength of the ceramic substrate.
On the outer surface of the closure plate 66 are formed suitable
films of the upper and lower electrodes 75, 77 and the
piezoelectric/electrostrictive layers 79, by any one of various
known methods which include thick-film forming process such as
screen printing, spraying, dipping and coating, and thin-film
forming process such as ion-beam method, sputtering, vacuum vapor
deposition, ion plating, CVD and plating. These layers 75, 77, 79
may be formed either before or after firing of the closure plate 66
(the ink pump member 44). Then, the electrode films 75, 77 and
piezoelectric/electrostrictive layer 79 thus formed on the closure
plate 66 may be heat-treated as needed, either in different steps
following formation of the respective layers 75, 77, 79, or in one
step following formation of all of the layer 75, 77, 79. To assure
improved reliability of insulation between the electrode films 75,
77, there may be formed as needed an insulating resin layer between
the adjacent piezoelectric/electrostrictive layers 79, 79.
The electrode films 75, 77 of each piezoelectric/electrostrictive
unit may be formed of any electrically conductive material which
can withstand a high-temperature oxidizing atmosphere generated
upon the heat-treatment or firing as described above. For instance,
the electrode films 75, 77 may be formed of a single metal, an
alloy of metals, a mixture of a metal or alloy and an electrically
insulating ceramic or glass, or an electrically conductive ceramic.
Preferably, the electrode material has as a major component a noble
metal having a high melting point, such as platinum, palladium or
rhodium, or an alloy such as silver-palladium alloy,
silver-platinum alloy or platinum-palladium alloy.
The piezoelectric/electrostrictive layer 79 of each
piezoelectric/electrostrictive unit may be formed of any
piezoelectric or electrostrictive material which produces a
relatively large amount of strain or displacement due to the
converse or reverse piezoelectric effect or the electrostrictive
effect. The piezoelectric/electrostrictive material may be either a
crystalline material or an amorphous material, and may be a
semi-conductor material or a dielectric or ferroelectric ceramic
material. Further, the piezoelectric/electrostrictive material may
either require a treatment for initial polarization or poling, or
may not require such a polarization treatment.
The piezoelectric/electrostrictive material used for the
piezoelectric/electrostrictive layer 79 preferably contains as a
major component lead zirconate titanate (PZT), lead magnesium
niobate (PMN), lead nickel niobate (PNN), lead manganese niobate,
lead antimony stannate, lead zinc niobate, lead titanate, or a
mixture thereof. The piezoelectric/electrostrictive material having
the above major component may further contain as an additive an
oxide or other compound of lanthanum, barium, niobium, zinc,
cerium, cadnium, chromium, cobalt, strontium, antimony, iron,
yttrium, tantalum, tungsten, nickel, and/or manganese, so as to
provide a material containing PLZT, for example.
The piezoelectric/electrostrictive unit consisting of the electrode
films 75, 77 and the piezoelectric/electrostrictive layer 79
generally has a thickness of not larger than 100 .mu.m. The
thickness of each of the electrode films 75, 77 is generally 20
.mu.m or smaller, preferably 5 .mu.m or smaller. To assure a
relatively large amount of displacement by application of a
relatively low voltage, the thickness of the
piezoelectric/electrostrictive layer 79 is preferably 50 .mu.m or
smaller, more preferably, within a range of 3 .mu.m to 40
.mu.m.
Since the substrate of the piezoelectric/electrostrictive element
78 is constituted by the closure plate 66 formed of a material
having partially stabilized zirconia as a major component, the
element 78 exhibits sufficiently high degrees of mechanical
strength and toughness even though the plate 66 has a relatively
small thickness. At the same time, the thus formed
piezoelectric/electrostrictive element 78 can provide a relatively
large amount of displacement by application of a relatively low
operating voltage, with a relatively large magnitude of force or
electric potential generated, and has an improved operating
response.
In addition, the film-forming method used for forming the electrode
films 75, 77 and the piezoelectric/electrostrictive layer 79
permits a relatively large number of the
piezoelectric/electrostrictive elements 78 to be formed on the
closure plate 66 of the ink pump member 44. That is, in the
film-forming process as described above, the elements 78 can be
concurrently and easily formed with a minute spacing left between
the adjacent ones, without using an adhesive or the like.
Accordingly, a plurality of piezoelectric/electrostrictive elements
78 can be easily formed on appropriation portions of the ink pump
member 44 which correspond to the respective ink chambers 46 formed
therein.
After firing the above-described ink pump member 44 on which the
piezoelectric/electrostrictive elements 78 are integrally formed,
the ink pump member 44 is superposed on the above-described ink
nozzle member 42, and these members 42, 44 are bonded together by a
suitable adhesive, into an integral structure of the ink jet print
head 40, as shown in FIG. 1. In the thus formed ink jet print head
40, the ink material which is led through the ink supply channel 62
is supplied to the ink chambers 46 through the respective orifices
58, and is passed through the through-holes 56, 57 and jetted
outwards from the nozzles 54, based on the operation of the
piezoelectric/electrostrictive elements 78 formed integrally on the
ink pump member 44.
The adhesive used for bonding the ink pump member 44 and ink nozzle
member 42 may be selected from various known adhesives containing
any one of vinyl, acryl, polyamide, phenol, resorcinol, urea,
melamine, polyester, epoxy, furan, polyurethane, silicone, rubber,
polyimide and polyolefin, provided the selected adhesive is
resistant to the ink material.
It is desirable in terms of production efficiency that the adhesive
is in the form of a highly viscous paste which can be applied by
coating using a dispenser, or by screen-printing, or is in the form
of a sheet which permits punching thereof. It is more desirable to
use a hot-melt type adhesive which requires a relatively short
heating time, or an adhesive which is curable at room temperature.
The adhesive in the form of a highly viscous paste may be obtained
by mixing an adhesive material with a filler so as to increase the
viscosity of the resulting adhesive.
In view of the durability with respect to an aqueous ink material,
it is particularly preferable to use an elastic epoxy adhesive or
silicone-contained adhesive which can be applied by
screen-printing, or sheet-like, hot-melt type adhesive containing
polyolefin or polyester, which permits punching thereof. It is also
possible to apply various adhesives as indicated above to different
portions of the bonding surfaces of the ink pump member 44 and/or
the ink nozzle member 42.
Upon bonding of the ink pump member 44 and ink nozzle member 42 as
described above, the ink chambers 46 formed in the ink pump member
44 are suitably held in communication with the nozzles 54 and the
ink supply channel 62 formed in the ink nozzle member 42, with the
first and second communication holes 72, 74 being in communication
with the through-holes 56 and orifices 58 formed through the
orifice plate 50 of the ink nozzle member 42, respectively.
To achieve sufficient fluid-tightness of the ink flow channel
through which the ink flows in the print head 40, the seal between
the bonding surfaces of the ink pump member 44 and the ink nozzle
member 42 needs to be well established only at around the first and
second communication holes 72, 74. This leads to a significantly
reduced area of bonded portions which must provide a complete seal,
permitting the ink flow channel to easily and surely assure
excellent fluid-tightness.
In this particular embodiment, the diameters of the first and
second communication holes 72, 74 are set to be smaller than the
width dimension of the ink chamber 46 (the width dimension of the
window 76 formed in the spacer plate 70). Therefore, the adjacent
ones of the first communication holes 72 and those of the second
communication holes 74 are spaced apart from each other by a
sufficiently large distance (indicated by "L" in FIG. 2).
The above arrangement assures a sufficiently large area of bonding
between the ink pump member 44 and the ink nozzle member 42, at
around the respective first and second communication holes 72, 74.
Accordingly, a further improved seal can be obtained at the bonding
surfaces of the members 42, 44 even if these members 42, 44 are
made of different kinds of materials.
Depending upon the kind of the adhesive used or the method of
application of the adhesive, there is a possibility that the
adhesive would overflow into the first and second communication
holes 72, 74 to thereby close the openings of these holes 72, 74.
In this case, it is desirable that the diameter of the first and
second communication holes 72, 74 be set to be substantially equal
to the width dimension of the corresponding ink chamber 46, so as
to avoid the closure of the openings of the holes 72, 74. It is
also desirable to form one or both of the first and second
communication holes 72 in teardrop shape as shown in FIG. 7, or
elliptic shape.
It will be easily understood by comparing the shapes of the bonding
surfaces of the ink nozzle member 42 and the ink pump member 44 of
the ink jet print head 40 of the instant embodiment, with those of
the ink nozzle member 16 and the ink pump member 24 of the
conventional ink jet print head as shown in FIGS. 5 and 6 that the
print head 40 of the instant embodiment can achieve a significantly
improved seal at the bonding surfaces of the members 42, 44, as
compared with the conventional counterpart as shown in FIGS. 5 and
6.
Accordingly, the ink jet print head 40 can easily and stably assure
sufficient sealing or fluid-tightness of the ink flow channel
through which the ink flows, without suffering from the overflow of
the adhesive into the ink chambers 46, and otherwise possible gaps
formed between the bonding surfaces. Thus, the ink jet print head
40 exhibits significantly improved ink-jetting characteristics.
In producing the ink jet print head 40 as described above, a
suitable film-forming method is employed to form the
piezoelectric/electrostrictive elements 78 each of which is adapted
to deform a portion of the closure member 66 which defines the
corresponding ink chamber 46 to thereby change the internal
pressure of the ink chamber 46. Therefore, the
piezoelectric/electrostrictive elements 78 can be easily formed on
the portions of the closure member 66 which correspond to the
respective ink chambers 46, with high production efficiency,
assuring excellent ink-jetting characteristics of the print head
with high stability.
While the present invention has been described in its presently
preferred embodiment with a certain degree of particularity, it is
to be understood that the invention is not limited to the details
of the illustrated embodiment, but may be otherwise embodied.
While the ink supply channel 62 through which the ink is fed into
the ink chambers 46 is formed within the ink nozzle member 42 in
the illustrated embodiment, the ink supply channel 62 may be formed
within the ink pump member 44, as shown in FIG. 4 by way of
example. In this figure, the same numerals as used in FIG. 1
showing the first embodiment are used for identifying structurally
or functionally corresponding elements, so as to facilitate
understanding of the embodiment of FIG. 4.
The structure and material of the ink nozzle member 42 are by no
means limited to those of the illustrated embodiment. For instance,
it is possible to form the whole or a part of the ink nozzle member
42 as an integral body, by injection molding using a synthetic
resin material or the like, or any other molding technique.
Further, the position and number of the nozzles 54 and orifices 58
formed in the ink nozzle member 42, and the position and number of
the ink chambers 46 formed in the ink pump member 44 are never
limited to those of the illustrated embodiment, but may be suitably
selected.
Moreover, the principle of the present invention is applicable to
ink jet print heads of on-demand type or continuous jet type, and
to these types of ink jet print heads having various
structures.
It is also to be understood that the present invention may be
embodied with various other changes, modifications and
improvements, which may occur to those skilled in the art, without
departing from the spirit and scope of the invention defined in the
following claims.
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